1. Microfiche Appendix
This patent disclosure includes a computer program in a microfiche appendix which has 173 total frames and 2 fiche.
2. Field of the Invention
This invention relates to editing video tape by a computer-based system which includes a random access memory device such as a disk drive. More specifically, the invention relates a method and apparatus for storing portions of video taped material on disk and using the information on the disk to edit the taped material. In one embodiment, the computer platform is a Macintosh computer.
3. Description of the Prior Art
Various methods of video tape editing are well known in the art. Traditional editing is tape-based; the editor cycles tapes back and forth on a source VCR (video cassette recorder) or VTR (video tape recorder) to find the scene that he means to edit. He positions the record (destination) tape on the record (destination) VCR to receive the scene from the source tape. Then the scene from the source tape is recorded on the record tape; this process is repeated for each successive scene. This linear process requires constant cycling of tapes.
Also known is disk-based editing wherein a computer system including a random storage rotating memory device such as a hard disk drive, optical, or magneto-optical disk drive. All the video material is stored on a disk drive controllable by a computer used as an editor. Then random access of the disk via the computer finds any frame in the stored video material virtually instantaneously. The computer keeps track of all the edit and record frames for the entire production. When the edit decisions of the program are completed, the editor inserts source tapes in one or more VTR's and a new record tape into the record VCR and the computer executing the edit decision list created when using the disk video records the entire edited program onto the tape. Disk-based editing is fast, easy, and vastly reduces tape handling and is currently used by professional editing companies and movie studios.
However, even with such professional systems, the problem remains that a disk drive can only store a very short amount of video material. Typically, 300 megabytes or more of disk storage are needed to edit even a relatively short 10 minute program or film. Also, fast access disks (such as 16 milliseconds or less) are needed. This prohibits use of typical magneto-optical disks. Thus the disk-based systems are expensive and need large amounts of disk storage.
Additionally, disk-based editing typically requires logging the video material from the tape onto the disk which is a separate and time consuming step. This step is especially problematic when many hours of video material are available, such as when editing a film in which typically 10 to 20 times as much material is recorded as is needed for the final production. In this case, disk-based editing is virtually impossible except for short segments of the project. For instance, it requires 22 megabytes of disk capacity to store one minute of highly compressed source video. One hour of source video therefore requires approximately 1.3 gigabytes of storage. Thus even a very expensive disk-based system is not capable of storing a large amount of video recorded material. Without compression of the video, the cost of disk storage would rise dramatically. One commercial system costing $60,000 stores only 25 seconds of uncompressed video. The effects of compression result in significantly degrading the quality of the video signal to the point of making it impossible to make critical edit decisions.
Therefore, the prior art systems suffer from the deficiency in the on-line system using physical tapes of having very slow access times, and in the case of the off-line disk-based systems, of being quite expensive and also only allowing the editor to work with a limited amount of video material at any one time and with reduced video quality. Additionally, the disk-based systems have the deficiency of requiring a separate step of logging the video material onto the disk and then after editing of generating an edit list and using that to edit the actual video tape.